The above workpiece conveying equipment is known in automobile assembly lines, for example. The automobile assembly lines for example are configured such that on a first conveying path constituting a trim line or final line where work with respect to a relatively low region of the periphery of an automobile body supported on a conveying carriage is performed, the conveying carriage is made to travel in a longitudinal orientation parallel to the front-rear direction of the supported automobile body, and on a second conveying path constituting a chassis line where work of assembling an engine or an axle unit from beneath the automobile body is performed, the conveying carriage is made to travel in a transverse orientation orthogonal to the front-rear direction of the supported automobile body. Meanwhile, a worker gets on the conveying carriage which supports the automobile body and carries out a required work while walking around the periphery of the supported automobile body on the first conveying path. Therefore, a large conveying carriage having a working floor thereon projecting also before and after the supported automobile body is required. On the second conveying path, on the other hand, attachment-loaded carriages having been loaded with heavy materials such as engines and axle units are entered under the front and rear of the automobile body, and then required works are carried out. For the conveying carriage which travels sideways on this second conveying path, a compact conveying carriage without a working floor projecting laterally in the carriage traveling direction from the front and rear of the automobile body is more favorable since the need to make the heavy attachment-loaded carriages get on and off the conveying carriage is eliminated.
From the above viewpoint, it is conceivable to use a variable-length conveying carriage capable of traveling as a long conveying carriage being long in the front-rear direction at the time of traveling longitudinally on the first conveying path and also capable of shortening the length of the carriage in the front-rear direction corresponding to the left-right direction with respect to the sideways traveling direction at the time of traveling sideways on the second conveying path, or to use a long conveying carriage being long in the front-rear direction and dedicated to the first conveying path and a short conveying carriage being short in the front-rear direction and dedicated to the second conveying path and then to transship the automobile body between the long and the short conveying carriages. As the conventional variable-length conveying carriage usable in the automobile assembly line as described above, there have been known a conveying carriage provided with auxiliary stands before and after a conveying carriage main body thereof which slidably move in and out (a conveying carriage as described in Patent Document 1) and a conveying carriage pivotally supporting auxiliary stands before and after a conveying carriage main body thereof so as to rise and fall, etc.    Patent Document 1: Japanese Published Unexamined Patent Application No. H04-362459